PROBABLE CAUSE: "The pilot continued to fly VFR into unfavourable weather over the jagged shoreline with practically zero visibility due to heavy rain. There was a heavy squall at the time and at the scene of the accident. Weather conditions in the Western Mindanao area during the day of the accident were generally unfavourable for VFR flights. When the pilot took off from Siocon the ceiling at the destination, Zamboanga, was below IFR minima."